Q89 — Vital Bus Inverter LCO 3.0.3
062 AC Electrical Distribution - G2.2.42 (4.6)
REFERENCE PROVIDED
Given:
• Unit 2 is at 100% Reactor Power
At time 09:00 on June 12
• The Vital Instrument Bus 2A Inverter is declared inoperable
At time 09:30 on June 12
• The 2A Vital Instrument Bus is now being powered from its alternate power source
At time 12:00 on June 12
• The Vital Instrument Bus 2D Inverter is declared inoperable
At time 12:30 on June 12
• The 2D Vital Instrument Bus is now being powered from its alternate power source
In accordance with Unit 2 Technical Specifications, which ONE of the following completes the statement below?
If BOTH Inverters remain inoperable, then ___ is the LATEST Time / Date that Unit 2 is required to be in HOT STANDBY.
Given:
• Unit 2 is at 100% Reactor Power
At time 09:00 on June 12
• The Vital Instrument Bus 2A Inverter is declared inoperable
At time 09:30 on June 12
• The 2A Vital Instrument Bus is now being powered from its alternate power source
At time 12:00 on June 12
• The Vital Instrument Bus 2D Inverter is declared inoperable
At time 12:30 on June 12
• The 2D Vital Instrument Bus is now being powered from its alternate power source
In accordance with Unit 2 Technical Specifications, which ONE of the following completes the statement below?
If BOTH Inverters remain inoperable, then ___ is the LATEST Time / Date that Unit 2 is required to be in HOT STANDBY.
A. 18:00 on June 12
B. 19:00 on June 12
C. 18:00 on June 13
D. 18:00 on June 15
▶ Show Answer & Explanation
✓ B. Correct. Based on the question stem, at 0900 on June 12, the crew must perform LCO 3.8.2.1 (Required Action A). At 1200 on June 12 and with 2 inverters now inoperable, the crew must now perform LCO 3.0.3 (since there is no REQUIRED ACTION of LCO 3.8.2.1 for 2 inoperable inverters). LCO 3.0.3 requires the Unit to be placed in HOT STANDBY within a maximum of 7 hours (1200 on June 12 + 7 hours = 1900 on June 12).
✗ A. Incorrect but plausible. 18:00 on June 12 is the time/date if the candidate correctly determines that LCO 3.0.3 is applicable but incorrectly determines that LCO 3.0.3 allows only 6 hours to be in HOT STANDBY.
✗ C. Incorrect but plausible. 18:00 on June 13 is the time/date to restore the inverter to OPERABLE status IAW LCO 3.8.2 REQUIRED ACTION B.
✗ D. Incorrect but plausible. 18:00 on June 15 is the time/date to place the Unit in HOT STANDBY IAW LCO 3.8.2 REQUIRED ACTION B (if 2D Inverter remains inoperable).
Ref: LCO 3.8.2.1, LCO 3.0.3 | LO: NOS05TECHSPEC-12 — Describe the general requirements associated with Specifications 3.0.1 through 3.0.6 | Source: Bank — LOR 2018 Bi-Annual Crew D Written Exam SRO Q33 | Cognitive: Higher
Connections
- Related systems: 115V AC
- Related tech specs: TS 3/4.8 — Electrical, TS 3/4.0 — Applicability
- Related exam: 2019 NRC Written Exam